Past methods for obtaining water suitable for use in making soft drinks have employed a series of cumbersome procedures requiring large working areas and open systems highly susceptible to contamination and, hence, a need to add large amounts of chlorine to insure sterility of the water prior to the use of the treated water in bottling, for example, soft drinks. Distillation methods are a known alternative but are economically prohibitive for some large scale operations.
Most source water (including ground water or municipal water) contains amounts of salts such as sodium, calcium, magnesium and iron along with carbonates and particulate matter which make the source water unsuitable for use in bottling pure water or soft drinks. Of particular concern to the bottlers of soft drinks is the higher-than-desired content of carbonates in ground water obtained from municipal water supplies. The makers of soft drinks also require that the treated water be sterile to insure continued sterility of the soft drink product. Concentrated syrups used to make soft drinks contain a high concentration of sugar which would serve as an excellent growth substrate for the microbes should any be present in the water used in the bottling.
In order to rid the source water of the undesirable salts, particles and carbonates, one known method employs a first-step mixing procedure wherein source water is added to an open vat containing a mixture of calcium hydroxide, iron sulfate, lime and chlorine (sodium hypochlorite). The entire mixture is then stirred and allowed to settle. The calcium hydroxide, iron sulfate and lime serve to precipitate carbonate and bicarbonate ions as calcium salts, which settle to the bottom of the vat. The treated water is then siphoned off the top of the settled debris, which includes a mixture of calcium carbonate, calcium sulfate, iron oxide and lime. This debris must be disposed of. Typically, this sediment is disposed of down commercial drains for lack of alternate disposal systems. This disposal procedure is cumbersome and given the large quantities of water so treated, may create problems in subsequent municipal sewage treatment plants.
The foregoing procedure, also, fails to remove any of the sodium typically present in water supplies at about 200 parts per million. This first-stage mixing procedure may even result in an increased sodium content since sodium hypochlorite is typically added. Such a high sodium content makes this water unsuitable for individuals on sodium-restricted diets and may alter the taste of soft drinks prepared with this water.
Additionally, the use of an open vat which is highly susceptible to airborne microbial contamination necessitates the addition of large amounts, such as 15-20 parts per million of chlorine to insure sterility of the treated water. The added chlorine must then be moved as its presence would greatly interfere with the taste of the water so treated. It is undesirable to manufacture soft drinks from chlorine-containing water because the taste, color, and quality are adversely affected. The presence of even low concentrations of chlorine could make it impossible to achieve a soft drink product meeting quality standards. Present methods for removing the chlorine added in the first treatment step involve passing the first treated water through large closed tanks containing particles of sterile carbon.
This carbon treatment step currently employed is also undesirable as the activated carbon particles must be backflushed daily with treated water to remove residues, for example calcium carbonate, that coat and inactivate carbon. The backflushing process breaks down the carbon particles resulting in the necessity for carbon replacement at least once per year or more as needed. The entire tank, and its contents of carbon, sand and gravel must be sterilized regularly, at least once per week (or more depending on bacterial count) and the contents replaced periodically and additionally sterilized. Sterilization of the carbon particles is achieved by hot steam requiring an additional apparatus capable of flushing the carbon tanks with high pressure steam. Removal of the carbon from these tanks is a cumbersome, time-consuming, labor-intensive process and further necessitates the shut-down of the entire treatment process, sometimes for several days. As a result, water treatment rooms are often hot, unairconditionable, dusty, environments with occasional carbon black water-laden floors. It is difficult to keep such an environment sanitary. Additionally, since persons and objects are carriers of microbes, the introduction of large amounts of carbon, sand and gravel and high labor requirements of the burdensome process outlined above causes the introduction of numerous microorganisms to the tanks, equipment and the treatment room.
The requirement that large amounts of chlorine be employed also increases production costs in several ways. First a large capital investment in high-volume chlorine removal equipment is necessitated. Second, labor costs are greatly increased due to the extensive maintenance requirements of the necessary equipment and the labor-intensive sterilization procedure. Third, expenditures are increased for chlorine as the amount used is increased. Production costs are also increased due to chemicals used in the precipitation procedure, as they are both costly and expensive to store.
It was, therefore, desirable to develop a water treatment process which could remove the salts, iron, carbonates, sodium, particles, and any other undesirable materials from source water supplies, which treatment would not require the use of large quantities of sterile carbon to remove the high concentrations of chlorine which had to be added to water in prior methods. A need existed to develop a method for economically sterilizing large quantities of water, and delivering it sterile and chlorine-free to its end use. Finally, it was desirable to devise a method which would allow sanitary water treatment facilities to exist, to minimize the microbial contamination that would be brought into the plant, to reduce labor requirements, to eliminate shut-down time and undesirable treatment room conditions, and to develop a more economical process.